Fiat's unique system of computer-controlled intake valves allows a small car like the 500 to produce a surprising 101 hp and plenty of low-rpm torque.

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Engines are like people: The harder they work, the more air they need to breathe. When an engine is revved high, like when accelerating on the highway, its valves must open wide and for long durations. Conversely, at idle, that engine requires just a trickle of air to operate. Variable valve timing and lift systems continuously alter the way a valve operates, depending on engine speed and load, to increase fuel efficiency and power. These systems are becoming more common, but Fiat's Multiair is the most novel. It operates the intake valves with a unique system: Rather than using the cam lobe to press open the valve, the lobe pushes on the plunger of a tiny oil pump. The resultant pressure accumulates in a thimble-size chamber that feeds a computer-Â­controlled solenoid (the valve "conductor"). When the solenoid is open, the oil pressure flows to the top of the valve, forcing it to open. The engine computer directs the solenoid and can vary the timing (when the valve opens in relation to the piston's movement), duration, and lift (how far the valve opens). With Multiair, the tiny 1.4-liter engine of the Fiat 500 produces a gutsy 101 hp and a healthy amount of low-rpm torque. Also, since the system is simple and compact, it's not an expensive add-on. Expect Multiair to spread through Fiat's—and Chrysler's—lineup.